Gillespie, professor of American studies at Rutgers University, began researching his book, "Twin Towers: The Life of New York City's World Trade Center," in 1991. He wanted to explore the complex's cultural implications and symbolic meaning to Americans.

Before Sept. 11, only about 2,000 copies of the book had been sold by Rutgers University Press. Bookstores have now ordered more than 50,000 copies. Gillespie and the publisher are donating a portion of the profits to victims of the World Trade Center attacks.